The present invention relates to carton filling apparatus in general, and more particularly to improvements in apparatus of the type wherein the carton to be filled is inserted into a receptacle so that its open side faces upwardly and can receive a stack of paper sheets or the like, preferably from a container which is mounted at a level above the receptacle.
It is already known to provide the container above the receptacle for cartons with a bottom wall which is movable between open and closed positions so that a stack of sheets can drop by gravity into the empty carton therebelow as soon as the bottom wall is moved to open position. As a rule, the stacks constitute reams of 500 sheets each, i.e., the stacks are relatively low and the equally low side walls of the cartons for reception of such stacks exhibit a tendency to bulge outwardly and against the adjacent portions of the receptacle so that a stack can readily enter the carton therebelow. In other words, the size of the opening at the top of an empty carton is normally large enough to allow for unimpeded entry of the stack which descends from the container as soon as the bottom wall of the container is retracted or otherwise moved out of the way. Apparatus of such type are disclosed, for example, in U.S. Pat. No. 4,237,674 granted Dec. 9, 1980 to Aykut.
It was also proposed to assemble the bottom wall of the container from several panels which are pivoted downwardly into the open top of a carton therebelow so that the panels maintain the carton in requisite position for reception of a stack. A drawback of such apparatus is that each freshly filled carton must be lowered to a level below the panels of the bottom wall in order to enable the panels to reassume those positions in which they are capable of supporting a stack in the container. Lowering of filled cartons necessitates the use of additional equipment and slows down the rate at which the apparatus can fill successive cartons with stacks of paper sheets or the like. Therefore, apparatus wherein the bottom wall is retracted in a horizontal plane are preferred when cartons are to be filled at a high frequency. However, such apparatus are not satisfactory when a carton is to accommodate a relatively tall or very tall stack of paper sheets, e.g., a stack containing five reams of 500 sheets each or a single stack of, for example, 2500 sheets. This is due to the fact that a carton, whose side walls are sufficiently high to confine a stack of 2500 superimposed sheets, does not exhibit the required stability as to form, i.e., the side walls of the empty carton tend to bulge inwardly and to thus prevent unimpeded entry of a tall stack. Proposals to enhance the stability of cartons by making their walls of thicker and hence more rigid material are not favored by manufacturers and processors of paper sheets because such cartons are heavy, expensive and take up more room than standard cartons with relatively thin and hence flexible side walls.